(CNN) -- The Brazilian government is investigating the case of a 15-year-old girl who allegedly was raped and tortured after being put in a prison cell with 20 male inmates, officials said.
The girl -- who said she was forced to have sex for food and suffered burns and other abuse -- has denounced police in the small town of Abaetetuba for keeping her in the cell.
She is now in a witness protection program.
The case has sparked outrage among human rights groups as well as government officials.
"This is a shame, a shame in the whole system," said Claudio Puty, chief of staff for the governor's office in Para, one of the largest states in Brazil.
"There is a total collapse in the jail system in Brazil, but this is no excuse for them to wash their hands and do nothing," he said. "We are doing all we can to punish these policemen."
The victim -- who has been identified only by her initials, L.A.B. -- was jailed for attempted theft, and was sent to a police station in Abaetetuba, about 50 miles (80 kilometers) from the provincial capital of Belem, according to the O Liberal newspaper.
She remained in custody for about three weeks.
After receiving an anonymous phone call, two social workers tried to visit the girl in jail, but police barred them from doing so, the newspaper reported.
One of them, Maria Imaculada, told O Liberal the young woman was courageous and talked to them in front of several policemen.
In testimony before a tribunal, the girl told authorities she asked to speak to her relatives, but the police never responded, O Liberal reported, citing court documents. She testified that when she was forced into a bathroom, "I screamed and screamed, but to no avail," the report said.
The girl's father, who is also in a witness protection program, told reporters police asked him to forge the girl's birth certificate, but he refused. He said police threatened him and even questioned his paternity rights.
"She was humiliated and sexually assaulted in an Abaetetuba cell by those who should be defending her rights," he told O Liberal.
The Brazilian government has sent two commissions to investigate. Since the case made national headlines, other cases of women being sent to male prison cells have surfaced.
"What we are seeing here is endemic," Tim Cahill of Amnesty International said. 
Watch Cahill discuss a 'horrific' level of abuse »
Human rights groups and more than 16 local associations are planning a large protest this Sunday, the international Day for the Elimination of Violence Against Women. E-mail to a friend 
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